Acoustic device



Nov. 4, 1941. 'r. e. MOULDING 2,261,656

ACOUSTIC DEVICE Filed June 30, 1937 r inv g Q I I g i INVENTOR um; hm; THO/1A5 a. M001. D/A/G i BY 7, C

A TQRNEY Patented Nov. 4, 1941 UNITED STATES-PATENT OFFICE ACOUSTIC DEVICE Thomas G. Moulding, Toledo, Ohio Application June 30, 1937, Serial No. 151,219

2 Claims.

This invention relates to acoustic devices, more particularly to variable volume horns suitable for use with automobiles.

With the increasing velocity at which average automobiles move on the highway, the volume of sound emitted from a signal horn to give an effective warning signal has been greatly increased. The signal horn must be effective for greater distances due to the high velocity of the automobile in order to give ample time to the warned person to remove himself from the danger zone. When, however, the vehicle is moving at a relatively low rate of speed, such as, for example, driving within the limits of a city, the volume of sound emitted is disproportionate to the amount sufficient to give an effective warning signal. The loudness of the signal in many cases is an annoyance to persons living in the neighborhood, and in some cases has given rise to complaints which resulted in the suppression of the the use of horns.

This invention contemplates the provision of a signal device which may be adapted to suit the circumstances under which the vehicle is being operated, that is, if the speed is high, the signal device may be adjusted to emit a large volume of sound, on the other hand, if the speed is low, the volume may be adjusted to emit a relatively lower volume of sound. The adjustment may be accomplished by a manual means, but the invention'also contemplates an automatic controlling device to attain this purpose, a suitable function of the vehicle being selected to regulate the controlling means.

'It is, therefore, an object of this invention to provide an acoustic signalling device whose volume may be adjusted to suit the conditions under which an effective warning signal is to be given.

It is a further object of this invention to provide an acoustic device suitable for use on an automobile in which the volume of the horn may be controlled selectively by a manual means to change the magnetic fiux relations in the motor of the acoustic device to increase or decrease the effective flux to move the vibratile member of the acoustic device.

Other objects and advantages of this invention relating to the arrangement, operation and function of the related elements of the structure, to various details of construction, to combinations of parts and to economies of manufacture, will be apparent to those skilled in the art upon consideration of the following description and appended claims, reference being had to the accompanying drawing forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Figure 1 is an elevational View, partly in section, showinga horn to which the invention has been applied.

Figure 2 is a plan view of the coil used in the construction of Figure 1.

Figure 3 is a sectional elevational view taken along the line 3-3 of Figure 2.

Figures 4 and 5 are schematic diagrams of connections of the various modifications of the invention.

Referring to the drawing, particularly to Figure 1, there is shown an acoustic device having a base ill with an acoustical chamber [9A, a diaphragm H, and a motor mechanism 12 which drives the diaphragm H to produce sounds which issue from a bell l3. The motor mechanism I2 is provided with an armature M which is properly suspended for vibration and is connected to the diaphragm by means of a plunger rod 15, so that movements of the armature will vibrate the diaphragm. Cooperating with the plunger rod I5 is a circuit breaker mechanism It which cooperates with the armature i l in a well known manner which need not be described in detail. A resistance ISA is provided to shunt the circuitbreaker I6.

The motor mechanism 12 is provided with a magnetic actuating coil H which is positioned in a slot 18 in the stationary field member of the motor mechanism. As shown in Figure 1, the coil I1 is divided into two portions [1A and [1B as shown in detail in Figure 3, which cooperate to control the effectiveness of the motor mechanism I2 to oscillate the armature l4 and the diaphragm II.

The coil I! may be wound separately and positioned in the slot I8 during manufacture. The details of construction of the coil are shown in Figures 2 and. 3. Coils HA and [1B are properly insulated from each other and are held together by means of taping strips as shown. The leads from the individual coils project laterally from the upper side of the complete coil in the manner shown in Figure 2.

Referring again to Figure 1, a push button B, suitable for manual operation, is provided at any convenient position such as, for example, on the steering column of an automobile. The push button is designed to selectively open and/or close the circuits through the coils HA and NB, so that an operator may conveniently control the relations of the coils and thereby selectively attain the tonal quality desired of the acoustic device. The coils and the push button B are placed in circuit with a source of power and a well known relay device R (used to make the high current leads as short as possible) as shown in Figures 4 and 5.

In Figure 4, push button B closes the circuit through the actuating coil to the relay R which, in turn, attracts an armature to close the circuit through the actuating coil HA of the acoustic device. The coil MB is shown in circuit with a manual switch S, which is conveniently located on the dash board of the automobile, the switch S being operable at selected times to short-circuit the coil NB. The coil llB, which is in close juxtaposition with the actuating coil l (A in the slot 18 of the motor mechanism 12, will, when shortcircuited, absorb a substantial amount of energy which is flowing through the actuating coil llA, so that the flux, which, under normal circumstances with the coil llB open-circuited would actuate the armature I4 is dissipated and made inefiective to vibrate the armature.

A transformer action is set up between the coils, so that flux from the actuating coil llA will be used to create a short circuit current to flow in the coil [1B, which will dissipate the energy by heating and as the energy supplied to the coil HA is relatively constant, the energy available to vibrate the armature is necessarily diminished. The reason for this is not definitely known, inasmuch as it is a matter of design, but it may be explained by the assumption that the input may be limited by the number and duration of the closed periods of the interrupter which may remain fairly constant, due to the relation between the impedance of the coils, frequency of vibration of the armature, and the inertia of the moving parts. In this manner, an operator, by opening and closing the switch S, can determine the amount of energy which will be applied to the armature l4, and thereby determine the loudness and/ or timbre of the tone which issues from the acoustic device.

In Figure 5, a similar arrangement is shown,

except that the switch S is incorporated in the push button B, so that an operator may more conveniently close the respective circuits through the acoustic device to obtain the desired tone quality issuing from the acoustic device. The

push button B may be designed so that by being depressed a definite distance, the relay circuit will be closed to obtain the soft horn, and upon further depression, the coil IIB will be open circuited (in the initial stage, this circuit is preferably closed to short-circuit coil MB) to make the loud horn available.

Figures 4 and 5 illustrate the schematic connections of two identical horns which is the number commonly employed in automobiles. The use of two horns in no way changes the principle of operation of the individual horns and no reference has been made to the second horn.

It is to be understood that the above detailed description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of being practiced and carried out in various ways without departing from the spirit of the invention. The language used in the specification relating to the operation and function of the elements of the invention is employed for purposes of description and not of limitation, and it is not intended to limit the scope of the following claims beyond the requirements of the prior art.

What is claimed:

1. In a device of the class described, soundproducing means, motor means to actuate the sound-producing means comprising a fixed field element, a movable armature cooperating therewith, a pair of independent coils on the field element to influence the magnetic field produced by a current flow in at least one of the coils, and contact means cooperating with the armature to break the flow of current in one of the coils to cause vibratory movement of the armature, the

other coil when short-circuited being capable of absorbing energy to reduce the volume of the sound produced.

2. In a device of the class described, sound-producing means, motor means to actuate the soundproducing means comprising magnetic circuit means, coil means in an electric circuit for producing magnetic flux in the magnetic circuit means, armature means to cooperate with the magnetic circuit means, circuit-breaker means to break the circuit through the coil means to cause the armature to vibrate and actuate the sound-producing means, means inductively activated cooperating with the coil means to decrease the efiective magnetic flux to move the armature to actuate the sound-producing means and thereby decrease the volume of the sound-producing means.

THOMAS G. MOULDING. 

